17 KNOWLEDGE Chemical resistance of plastics With regard to chemical stability, plastics are classified as follows: + Very good chemical resistance Within 30 days, continuous exposure to media causes no damage to the plastic. The plastic may remain resistant for years. 0 Good to limited chemical resistance Within 7-30 days, continuous exposure to media causes minor damage (e.g. swelling, softening, loss of mechanical strength, discolouration), some of which is reversible. – Poor chemical resistance Not suitable for continuous exposure to media. Immediate damage may occur (e.g. loss of mechanical strength, deformation, discolouration, cracking, liquification). Chemical resistance of plastics to various substance classes Classes of substances at 20 °C PFA PTFE FEP ETFE PMP PP PE-HD PE-LD PC POM PA SAN PMMA PS PVC MF NR SI EPDM FKM Alcohols, aliphatics + + + + + + + + + + o + - + + + + + + - Ethers + + + + - o o o - + + - - - - - - - - - Aldehydes + + + + o + + o o o o - o - - + o o + + Esters + + + + o o o o - - + - o - - + o o o - Hydrocarbons, aliphatic + + + + o + + o o + o - + - + + - - - o Hydrocarbons, aromatic + + + + - o + o - + o - - - - + - - - o Hydrocarbons, halogenated + + + + - o o o - + o - - - - + - - - o Ketones + + + o o o o o - + + - - - - + - - o - Alkalis + + + + + + + + - + + + + + + - + o + o Acids, strong or concentrated + + + + + + + + - - - - - o + - - - + o Acids, weak or diluted + + + + + + + + o - - o - o + o o o + + Oxidising acids, oxidising agents + + + + - - - - - - - - - - - - - - o o The carefully prepared recommendations listed here are based on technical literature and made available by the manufacturers of raw materials, to provide information and advice. However, nothing can replace suitability tests conducted by the end user under the actual conditions of use.
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